$\begingroup$I recommend setting up a separate meta post where users propose tag synonyms (example ). The current "vote for synonyms" system is rather obscure and hard to use.$\endgroup$
– ManishearthJun 26 '13 at 17:26

$\begingroup$Because there's a high chance it will get too huge. But that's OK too, just specify "feel free to propose your synonyms as answers here" in the q :)$\endgroup$
– ManishearthJun 26 '13 at 17:28

$\begingroup$I've started creating tag excerpts for some of the tags. Feel free to decline, I'm not entirely sure of some. I may create tag wikis too, though they will be short. An idea tag wiki is a good intro to the topic, with links to common canonical questions and books.$\endgroup$
– ManishearthJun 26 '13 at 17:39

1

$\begingroup$I declined a few, @Manishearth. I expected you wouldn't be offended but it's nice to hear you confirm.$\endgroup$
– François G. Dorais♦Jun 26 '13 at 17:45

$\begingroup$Oh, sure :) I'm an outsider here, besides not being a mathematics researcher I have very little knowledge of what sort of questions get asked here. I'm only hanging around because I want to help you guys get back on your (2.0) feet :) So I don't expect to be right in these matters at all.$\endgroup$
– ManishearthJun 26 '13 at 17:47

$\begingroup$Does anyone have any template or suggestion for what should go on the extended tag wiki (not the excerpt)? Honestly, I don't even know where to start, as it feels like a wikipedia article.$\endgroup$
– Ricardo AndradeJun 27 '13 at 2:00

21 Answers
21

The excerpt is the elevator pitch for the tag. You only have ~500 plain text characters for the excerpt, so don’t feel obligated to cover everything in it! Save that for the 30,000+ character Markdown tag wiki. The excerpt should define the shared quality of questions containing this tag — boiled down to a few short sentences.

Avoid generically defining the concept behind a tag, unless it is highly specialized. The “email” tag, for example, does not need to explain what email is. I think we can safely assume most internet users know what email is; there’s no value in a boilerplate explanation of email to anyone.

Concentrate on what a tag means to your community. For “email” on Server Fault, mention the server aspects of email including POP3, SMTP, IMAP, and server software. For “email” on Super User, mention desktop email clients and explicitly exclude webmail, as that would be more appropriate for webapps.stackexchange.com.

Provide basic guidance on when to use the tag. In other words, what kinds of questions should have this tag? Tags only exist as ways of organizing questions, so if we don’t provide proper guidance on which questions need this tag, they won’t get tagged at all, rendering the tag excerpt moot. Think of it as a sales pitch: in a room full of tags screaming “pick me!”, what would convince a question asker to select your tag?

Some tags are common knowledge. Most tags require a bit of explanation in the excerpt, even if it’s only 3 or 4 words. But if the tag is common knowledge — that is, if you walked up to any random person on the street and said the tag word to them, and they would know what you were talking about — then don’t bother explaining the tag at all. Stick to usage of the tag within your community in the excerpt.

We just got a question tagged icm-2014 and we have icm-2010 (with two closed questions tagged with it).

I think it is not necessary to have separate tags here and one ICMs tag should suffice.

Actually, I do not even think this ICM tag is necessary, conferences should suffice.

The numbers of questions involved here are small, but I rather would like to avoid reactivating the old icm-2010 questions, thus this request for merging or synonyming. (Also I do not want to retag icm-2014 manually if ever there is then opposition to the merge.)

$\begingroup$I think this is a good suggestion. However, I wonder if a new answer in this thread with lots of other answers still attracts significant attention...$\endgroup$
– Ricardo AndradeOct 17 '13 at 19:35

$\begingroup$Likely not significant one @RicardoAndrade, but basically it suffices if François G. Dorais (or another moderator) notices.$\endgroup$
– user9072Oct 17 '13 at 22:23

There are tags lattices and lattice-theory, both being used for the two unrelated meanings “partial order with binary suprema and infima” and “discrete subgroup of $\mathbb R^n$”. I’m not sure it’s feasible to sort out the ~300 questions involved, but maybe we could try at least to alleviate the problem for future by deciding which tag is supposed to denote which meaning, renaming them unambiguously, and supplying tag summaries. If not, the tags should be merged.

$\begingroup$Perhaps lattices-Zn and lattices-minmax might help? This is definitely a case where a short modifier would be useful. Gerhard "Using Algebraic Lattices Is Confusing" Paseman, 2014.06.26$\endgroup$
– Gerhard PasemanJun 26 '14 at 17:38

$\begingroup$@GerhardPaseman yes something along these lines. However, I would prefer other disambiguations (the usage of Wikipedia seems a good model).// Also it might be worth noting there is a tag euclidean-lattices and also lattice in the alg sense can be used more general than disc subgroups of R^n or someting iso to Z^n.$\endgroup$
– user9072Jun 26 '14 at 18:45

$\begingroup$Thanks for the link, I had a vague recollection this was discussed before, but couldn’t find it. However, @quid, I am quite confused by your comments both here and there. The post tea.mathoverflow.net/discussion/1375 discusses exactly the same distinction as here (“lattice as an algebraic structure” is the same thing as “lattice as a poset”, just formulated in a different signature). You somehow seem to call “algebraic” what everyone else in the discussion calls “geometric”, or otherwise I can’t make heads or tails of the last sentence in your post here. Could you please clarify?$\endgroup$
– Emil JeřábekJun 27 '14 at 10:01

$\begingroup$@EmilJeřábek in tea.mathoverflow.net/discussion/679/lattices it was suggested by Ryan Budney to have lattice-poset and lattice-subgroup, mentioning Wikipedia, and I agree this is a good idea. I refered to the latter as algebraic (perhaps this is a bad/confusing idea though) and would call geometric only special cases of it, like the one you mention, for which there is more or less a tag already namely euclidean-lattices (though one might generalize the name a bit to point-lattices as suggested in the tea thread you link to).$\endgroup$
– user9072Jun 27 '14 at 10:31

$\begingroup$I should however add that I do not have a fixed opinion here, also what I suggest might still miss out on some lattices in the sense of modules (and I somehow lumped this into the 'algebraic'), and I feel I do not fully oversee the situation. The main point I wanted to make here, in view of your proposal and Gerhard Paseman's comment is that not every use of lattice that is not the partial order meaning is captured well by the second tag proposed, and indeed for what you seem to propose, there mainly is a tag already (namely euclidean-lattices).$\endgroup$
– user9072Jun 27 '14 at 10:48

$\begingroup$That’s not what I want to propose, I want to disambiguate the existing two mixed-up tags into two categories as broad as possible. Above I was just trying to figure out your terminology, so that we are both talking about the same thing, I didn’t mean to restrict the second category to sublattices of $\mathbb R^n$. Ryan Budney’s proposal looks fine to me. “Lattice-poset” is not ideal as more often than not, they are considered as algebraic rather than order-theoretic structures, but in view of your comments, “lattice-subgroup” can also be interpreted as algebraic, so one needs another ...$\endgroup$
– Emil JeřábekJun 27 '14 at 11:22

$\begingroup$... word, and “poset” should do the job. Whether “lattice-subgroup” is an adequate description for the second meaning I can’t tell, as I am not much familiar with this field, but if it looks good to you, I’d go with it.$\endgroup$
– Emil JeřábekJun 27 '14 at 11:26

$\begingroup$I agree this should be the main concern. On second thought lattice-subgroup could have the issue to be read as "lattice of subgroups" , which would be quite unfortuante. Not sure how to call it. Perhaps we could simply use certain languages other than English and the problem will be trivial :-)$\endgroup$
– user9072Jun 27 '14 at 12:22

$\begingroup$Hmm, that’s a good point. Dropping the “sub” might help, but then again, “lattice-group” could be easily misinterpreted as referring to l-groups. Maybe “lattice-module”? (Though that sounds dangerously close to modular lattices. Oh dear.)$\endgroup$
– Emil JeřábekJun 27 '14 at 13:30

$\begingroup$I only see two questions with lattice-theory tags that involve free abelian groups with quadratic forms.$\endgroup$
– S. Carnahan♦Jul 1 '14 at 5:38

$\begingroup$@S. Carnahan: I see three (out of the 29 total, a substantial fraction of which is dual tagged). The real problem is the lattices tag, which contains many questions of both kinds.$\endgroup$
– Emil JeřábekJul 2 '14 at 14:47

1

$\begingroup$I indeed think that lattice-theory should be changed to lattice-ordering. As regards lattices, maybe lattices-discrete-subgroups? it's a bit lengthy but takes into account various ambiguities. It also takes into account the increasing research on discrete subgroups of Lie groups beyond the lattice case.$\endgroup$
– YCorFeb 23 at 12:02

I have noticed that the tag duality is quite often used for questions about dual spaces in functional analysis and linear algebra. However, it's not immediately clear from the tag name that this is intended. (Although the current revision of the tag-excerpt explicitly mentions dual spaces.)

I suggest to create a separate tag dual-spaces for questions about dual spaces of vector spaces, linear normed spaces, etc.

Perhaps it is worth mentioning in connection with this that there already exists tag called dual-pairs which might be used in context of functional analysis. (But from the usage it seems that it is used in other meanings, too. The tag-info is empty at the moment.)

$\begingroup$i'll add that if the consensus is that (duality) should be used for dual spaces, then perhaps creating a synonym (dual-spaces) $\to$ (duality) would be a reasonable thing to do. And the same thing applies if the consensus is that (dual-pairs) is the tag which should be used for questions about dual spaces.$\endgroup$
– Martin SleziakAug 27 '17 at 12:50

Tag 'kahler': I was wondering if the tag 'kahler' should be renamed 'kahler-manifolds' (or something like it), so as to make it more descriptive and less prone to confusion. I have browsed through all the questions with the tag 'kahler' and all of them are indeed about Kähler manifolds. This means the renaming would be an easy process, but it may also mean that it is not necessary. Any opinions?

Update: The tag 'kahler' no longer exists and 'kahler-manifolds' now exists in its place.

Tag 'differential-graded-lie-a': Here is another suggestion that may or may not be desired. Due to the character limit for tags, some long tags may become hard to understand. The worst offender I have found so far is 'differential-graded-lie-a' (with only two questions). This could very well be made a synonym of 'dg-lie-algebras' if people think there is a benefit.

$\begingroup$More expressive is an improvement, so I am in favor of the rename; for example, while there is kahler-differentials somebody not aware/not paying attention could easily use kahler for Kähler differentials, too. And, then we'd have a mess. Better to rename while it is easy than to untangle it latter.$\endgroup$
– user9072Jul 24 '13 at 23:24

$\begingroup$@quid: Do you think creating a synonym 'kahler-manifolds' <--- 'kahler' would be the appropriate action in this case?$\endgroup$
– Ricardo AndradeJul 24 '13 at 23:32

2

$\begingroup$I think it should really be renamed (and just kahler should stop to exist). If kahler exists as synonym and somebody would use it instead of kahler-differentials it would somehow even be worse as they'd end up in kahler-manifolds. Or to put it differently why should then kahler be a synonym of kahler-manifolds and not of kahler-differentials instead.$\endgroup$
– user9072Jul 24 '13 at 23:44

$\begingroup$@quid: One last question due to my ignorance. Do the moderators still have the power to rename tags?$\endgroup$
– Ricardo AndradeJul 24 '13 at 23:48

2

$\begingroup$I think so. And looking around at meta.SO somehow confirms this. For example, only some weeks ago there was this meta.stackexchange.com/questions/182097/… Now this rename was declined by a mod there, but on the grounds that it is not good and not that it is in impossible.$\endgroup$
– user9072Jul 25 '13 at 0:01

2

$\begingroup$I think I created the kahler tag, and I think your suggestion to rename it kahler-manifolds is a good one. Do you think it should be kahler-manifolds or kähler-manifolds?$\endgroup$
– Michael AlbaneseJul 25 '13 at 7:28

$\begingroup$@Michael: Are umlauts (or any other accents) even allowed in tags? Even if they are, it might still be best to not use them. Does anyone else have any opinions on the umlauts/accents?$\endgroup$
– Ricardo AndradeJul 25 '13 at 7:46

1

$\begingroup$@MichaelAlbanese umlauts and other specal characters do not work in tags; there was a discussion on the old meta if it should be kaehler instead, using the official way to transcribe umlauts, but it was decided to stick to kahler.// On the general question raised by Ricardo Andrade there is this discussion meta.mathoverflow.net/questions/390/spelling-conventions$\endgroup$
– user9072Jul 25 '13 at 11:17

$\begingroup$@quid: Do you think it would help to create a new meta thread to discuss renaming of tags such as the ones I proposed in this answer?$\endgroup$
– Ricardo AndradeAug 20 '13 at 6:25

1

$\begingroup$Once this one becomes too crowed with answers likely a new one could be good. Not sure if this is yet the case. But it seems good it was reactivated by a new answer. What I thought about recently was to create a chat-room for editing/tagging related issues.$\endgroup$
– user9072Aug 20 '13 at 12:43

$\begingroup$Thanks, @quid. The chat room idea is truly very interesting. I think it could be very useful to allow freer discussion of these issues, which sometimes lead to long discussions in the comments :) . Are you thinking about creating the chat room yourself? Are there any issues to work out first?$\endgroup$
– Ricardo AndradeAug 20 '13 at 22:28

$\begingroup$Yes, I thought about creating one since some time. The main issue to work out was if anybody but me would use it. :-) Other than that I think it is relatively straight forward to create a room though I do not know exactly how at this very moment. (But I will check.)$\endgroup$
– user9072Aug 21 '13 at 6:45

1

$\begingroup$Creating it was rather trivial, so I did it MO editors' lounge. That would have been another issue, a good name...but well we can edit it later :-)$\endgroup$
– user9072Aug 21 '13 at 7:01

For questions related to divisors in the sense of algebraic geometry (Cartier divisors, Weil divisors and so on). For question on divisors in the number theoretic sense please use the tag divisors-multiples.

Still, some people might not notice the tag-excerpt, and if they look only at the name of the tag they might assume that the words is used in number-theoretic meaning. (For example, the questions which are currently tagged divisors+nt.number-theory are most likely mistagged. And there are a few more examples of questions which originally had (divisors) tag and it was later corrected to (divisors-multiples) tag.)

I am not really sure what would be a good name for the tag. So I'd be grateful if you have some reasonable suggestions in comments.

$\begingroup$There are two types of divisors, Weil divisors and Cartier divisors. Algebraic cycles generalize (and fully subsume) Weil divisors, but in general Cartier divisors may be different and there is no analogous generalization (to my knowledge).$\endgroup$
– Joe BernerJan 25 '18 at 14:58

Based on the reception of the question Pronunciation questions (currently at score 22) it seems that questions about pronunciation are on-topic on this site (within some reasonable limits).

I suggest creating pronunciation tag for questions asking about pronunciation of mathematical terms, mathematical symbols and notation, names of mathematicians, etc. If we have a tag for such questions, this would make easier for the poster of a new question to check whether his question has been asked before.

To me (as an outsider, but still a bit interested in this topic) it seems that continuum theory is an area of general topology which enjoys some interest both among topologists and among mathematicians in general. (For example, one part of Open Problems in Topology is dedicated to continuum theory - 2 chapters in the first volume, 8 chapters in the second one.)

Quick search reveals several questions on the main with the word continuum or continua - of course, sometimes this word might be used in different meanings, but if you browse a bit among the search results you can see that several of those question are from this area or closely related to this topic.

We have convexity tag - it has empty tag wiki, but I understand the tag broadly as stuff related to convexity, convex functions, convex sets, etc. (Of course, for some of such questions convex-analysis or convex-geometry are more suitable.)

For some time there was concavity tag, see here. The tag was later deleted by an automated process which removed the tags which removes the tags used on single questions after certain time (unless the tag has a tag-wiki). As a result, the question where the tag was created is currently tagged untagged - since it was the only tag there.

I would suggest creating a synonym concavity $\to$ convexity. (After all, these two topics are very close.)

If somebody is willing to write tag-info for convexity, perhaps concavity could be mentioned there, too. (Since the questions in this tag are a bit diverse and I am not really sure what were the original intentions when the tag was created, I don't think I would be able to create a good tag-wiki with clear explanation when this tag is supposed to be used. So I will leave this to more experienced users.)

Mathematical questions related to mathematical software systems such as Sage, Mathematica, Maple, Pari/GP, and GAP. Note that troubleshooting questions are generally considered off-topic.

I think that one tag for both topics might be enough. It seems that at least some of questions in (software) tag are actually about (mathematical-software). (Probably depending on your definition what you consider mathematical software.) In both these tags we have some questions about various drawing tools - perhaps these can be considered mathematical software. Other than that, the only questions which are currently tagged software and where (mathematical-software) would be clearly bad fit are Tools for Organizing Papers? and What programming languages do mathematicians use?. (The latter is closed.)

I would suggest creating a synonym mathematical-sofware $\to$ software. (Choosing latter as a master tag simply because the name is more general, majority of the question is very likely be about mathematical software.)

If there are reasons to keep them separate, editing the tag-info for both tags to make the distinction clearer would be useful.

I will also mention that some programs have separate tag. For example, gap, sage, coq, magma, and maybe some others I did not notice.

$\begingroup$Somewhat related: On Mathematics site there is computer-algebra-systems tag. Would perhaps such tag useful on MO, too? (There is (computer-algebra) tag - which seems to have slightly different meaning and used; at least judging by the name and the tag-info.)$\endgroup$
– Martin SleziakSep 27 '17 at 10:15

$\begingroup$@FrançoisG.Dorais About your coq example - here is some related conversation with quid. My opinion is that it's ideal to include both the more specific tag (coq) and the more general tag (proof-assistants). The more specific tag helps better searching while the more general one has more followers, so it improves the chance that the question is seen.$\endgroup$
– Martin SleziakSep 28 '17 at 15:52

Looking at the main site, it seems that small uncountable cardinals (such as $\mathfrak p$, $\mathfrak t$, $\mathfrak b$, $\mathfrak d$, etc.) get quite a lot of attention on this site. For example, if you search for either of the cardinals mentioned before in the set theory tag, you can find a bunch of questions: p,
t,
b,
d.)

I think that creating a separate tag for this topic might made searching for such questions easier. Additionally people who are interested in the topic could follow the tag. (I.e., they could get those questions highlighted, they have easier access to recent questions in their favorite tags, etc.)

Of course, it is possible to consider also other candidates for the name of the tag. Wikipedia uses Cardinal characteristic of the continuum. (For example, cardinal-characteristic-continuum is under the 35 characters limit.)

If the consensus is that the tag small-uncountable-cardinals would be too specific and it is better not to create such tag, I would be grateful also for comments suggesting which tags can be used for questions where small uncountable cardinals are the main topic. In the past I have sometimes added infinite-combinatorics to such questions - was it a reasonable choice?

I think stone-cech should be a synonym of compactification (and the latter might be pluralized); at least I think stone-cech should be renamed to stone-cech-compactification (minus some characters to fit the limit).

$\begingroup$Unfortunately, 'stone-cech-compactification' has more than 25 characters. Nevertheless, I agree that the tag 'stone-cech' would be better with a reference to compactification; perhaps 'stone-cech-compactificat'? I also agree that the tag 'compactification' should be pluralized.$\endgroup$
– Ricardo AndradeFeb 17 '14 at 0:54

2

$\begingroup$On the other hand, the tag 'stone-cech' might be well-defined enough and sufficiently populated to not be adequate as a synonym of the tag 'compactification'. Maybe what we really need here is a new mechanism (beyond the existing synonym mechanism) for making some tags subordinate to others. In this case, we could make the tag 'stone-cech' subordinate to the tag 'compactification'.$\endgroup$
– Ricardo AndradeFeb 17 '14 at 0:56

2

$\begingroup$When I was about to pluralize prime number theorems, I realized that the phrase is too easily interpreted as "theorems about prime numbers" rather than "theorems about the distribution of prime numbers". Thoughts?$\endgroup$
– François G. Dorais♦Feb 17 '14 at 2:52

1

$\begingroup$@FrançoisG.Dorais a tag wiki should more or less solve this problem (I only did not write one before, since it depends a bit). But we could also create prime-number-distribution (or its plural) and synonymize both PNT and Dirichlet to it.$\endgroup$
– user9072Feb 17 '14 at 10:47

2

$\begingroup$And while we are pluralizing tags, can we please also pluralize the tag name 'configuration-space'?$\endgroup$
– Ricardo AndradeFeb 18 '14 at 7:23

1

$\begingroup$I oppose the synonym of dirichlet to PNT. Dirichlet has proven at least two theorems in his lifetime. We shouldn't prejudice toward analytic number theory.$\endgroup$
– Willie WongApr 25 '14 at 15:18

1

$\begingroup$@WillieWong this is a valid criticism, and also further reason to get rid of that tag. I'll remove it right away. (Oh! It turns out it is gone anyway. Not sure if retagged or auto deleted.)$\endgroup$
– user9072Apr 25 '14 at 15:25

$\begingroup$I will just point out that the limit for tag names was increased to 35. The tag is now called (stone-cech-compactification) and there is a synonym (stone-cech] $\to$ (stone-cech-compactification).$\endgroup$
– Martin SleziakSep 27 '17 at 9:59

$\begingroup$I hope there will be some feedback from other users on this. (Especially from the moderator who merged the two tags.) I will just point out that apart from a separate tag, also combination of the tags open-problems and big-list might be a reasonable way how to tag those questions (and how to search for them using tags).$\endgroup$
– Martin SleziakOct 15 '17 at 9:15

$\begingroup$It seems that there were slightly more than 40 questions tagged (open-problems-list) before the merge, and about 15 of them were tagged (big-list). So whichever solution is chosen (creating the tag open-problems-list again or using the big-list tag), it seems that about 30 questions have to be retagged manually if we want to get back to the status before the two tags were merged.$\endgroup$
– Martin SleziakOct 15 '17 at 9:16

$\begingroup$@MartinSleziak I do not think moderators should do such things without discussion.$\endgroup$
– Alexander ChervovOct 15 '17 at 11:33

$\begingroup$Just to make this visible also to other users, I'll mention that there was a brief discussion about this tag in chat: see here and here.$\endgroup$
– Martin SleziakOct 16 '17 at 11:45

$\begingroup$@MartinSleziak thank you for letting me know about that ! I posted a comment$\endgroup$
– Alexander ChervovOct 16 '17 at 19:06

There is a tag closed-questions on meta. If you look at the questions, some of them are not about questions which are already closed, but more about process of closing. (E.g., how is question closed, when it can/cannot be closed, etc.)

Make these two tags synonyms of each other. (Maybe (closing) could be the master tag, since it sounds a bit more general, but I do not have strong preference about the direction of the synonym.)

If there is some agreement that we should have both questions about closed questions and the process of closing questions under the same tag, this should be also added to the tag-excerpt/tag-wiki. And I think that on-hold questions could be included under the same tag.

I will add a comparison with other meta site - the one which I am most familiar with. On Mathematics Meta there are three separate tags closing, closed-questions and on-hold-questions. This sometimes makes users unsure which of the three tags to use.

I have noticed that there is a tag called interesting-tags on meta. It is actually one of the default tags - these are the tags that are automatically created on every new meta site and are not deleted even if they have zero questions.

You may notice that on Meta Stack Exchange, this tag is now a synonym of (favorite-tags). And I'd guess most users know this feature under the name favorite tags. (Maybe it was called differently at the time when the default tags were selected.) I think that average user would have hard time guessing what (interesting-tags) is intended for. Which might lead to inconsistent usage of this tag and some incorrectly tagged questions. (As you can see in this chat transcript the tag has been used on some question on meta - here and here - and in neither of the two cases in the intended meaning. To be honest, I was quite puzzled when I saw the tag for the first time.)

My suggestion is to clarify usage of this tag and also make the name correspond to today's terminology.

One possibility would be to create a new tag favorite-tags and make this tag a synonym. (With (favorite-tags) as the master tag. This would basically copy the usage on Meta Stack Exchange.)

Another option would be to create a tag synonym interesting-tags $\to$ favorites and use (favorites) both for favorite questions and favorite tags.

If you look at current usage of the tag favorites and also if you check current revision of the tag-excerpt and the tag-wiki, you can see that this tag is currently used for both favorite tags and favorite question. (I am partly to blame - I have used the tag in this way and also I have created the tag-info. However, it seemed to me a bit redundant to create a separate tag for favorite tags.)

This means that if we decide to have a separate tag for favorite-tags, this would require also retagging of a few older questions. Which is why I am inclined more to the latter option, i.e., to have one tag for both favorite tags and favorite question.

But I am certainly open to the other solution. We can discuss (and vote) in comments which of the two options is better.

On meta there are two tags searching and search. The latter is one of the default tags - these are the tags that are automatically created on every new meta site - which essentially means that it cannot be removed.

I would suggest creating a synonym search $\to$ searching. Having two tags for the same topic could lead to confusion which tag to choose and also to inconsistent usage of tags - and, consequently, this would make searching using tags a bit difficult.

I have mentioned this a few times in chat (October 2016, April 2018). Since I have not received any feedback there, I've decided to try my luck here on meta.

The tag analysis-and-odes has only five questions and empty tag info - so it does not seem to have any distinction from ca.classical-analysis-and-odes. Four of the five questions in this tag were asked by the same user, but since thy no longer have account on MathOverflow, we cannot even ask them whether their intention was to create something different from the existing top-level tag. For the list of questions, see here and here.

A reasonable alternative would probably be also to remove the tag manually, but a synonym solves the problem without bumping old question. And another advantage is that if somebody tries to create this tag in the future, it will automatically be changed to the ca.classical-analysis-and-odes tag.